In the recent fields of Digital Rights Management (DRM) technologies, a method of separately distributing (i) an encrypted content such as a music content and (ii) a rights object (in other words, rights information) to be utilized to use the encrypted content has been used. The rights object indicates designated constraint information such as counts at which the content is permitted to be used. The content is allowed to be used only within the constraints of the constraint information.
In the meanwhile, among mobile terminals such as mobile telephones, terminals for which memory cards can serve as external memories have been widely used. Therefore, the memory cards can hold data to be used by the terminals, for example. Such a terminal using a memory card as an external memory can store the above-mentioned rights object to the memory, when a content having a protected copyright is permitted to be used according to the rights object. However, if a rights object which is prohibited from being copied is copied to be stored in the memory card, rights of the rights object are allowed to be used in other terminals without permission. Therefore, a rights object is generally permitted to be moved only between the terminal and the memory card.
Patent Reference 1 discloses a method for moving a rights object from a memory card to a terminal. By the method of Patent Reference 1, the rights object is assigned with state information indicating whether the rights object is disabled (in other words, in a disabled state) or enabled (in other words, in an enabled state). Thereby, when the rights object is to be moved from the memory card to the terminal, the rights object in the memory card is disabled, and the disabled rights object is copied to the terminal. After copying, the rights object in the memory card is removed (in other words, deleted), and the rights object in the terminal is enabled.
During the above procedure, error would occur due to, for example, taking out of the memory card or power discontinuity. The terminal performs a recovery procedure for recovering a situation of the rights object from defects caused by the error.
FIG. 1 is a flowchart showing the recovery procedure in the prior art.
If an error occurs before the rights object is copied to the terminal (in other words, when the terminal does not have an enabled rights object) (No at 601), then disabled rights object in the memory card is enabled (602, 603). Thereby, a situation of the rights object is recovered to be in an original situation that is before the copying. If an error occurs after the rights object has been copied to the terminal (in other words, when the terminal has the enabled rights object) (Yes at 601), then the disabled rights object in the memory card is removed (deleted) (605). Thereby, the situation of the rights object is recovered to be in the situation that is after the copying.
[Patent Reference 1] Japanese Unexamined Patent Application Publication No. 2000-347946